path: root/doc/rfc/rfc9546.txt

Internet Engineering Task Force (IETF)                         G. Mirsky
Request for Comments: 9546                                      Ericsson
Category: Standards Track                                        M. Chen
ISSN: 2070-1721                                                   Huawei
                                                                B. Varga
                                                                Ericsson
                                                           February 2024


  Operations, Administration, and Maintenance (OAM) for Deterministic
              Networking (DetNet) with the MPLS Data Plane

Abstract

   This document defines format and usage principles of the
   Deterministic Networking (DetNet) service Associated Channel over a
   DetNet network with the MPLS data plane.  The DetNet service
   Associated Channel can be used to carry test packets of active
   Operations, Administration, and Maintenance (OAM) protocols that are
   used to detect DetNet failures and measure performance metrics.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9546.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
   2.  Conventions Used in This Document
     2.1.  Terminology and Acronyms
     2.2.  Key Words
   3.  Active OAM for DetNet Networks with the MPLS Data Plane
     3.1.  DetNet Active OAM Encapsulation
     3.2.  DetNet PREOF Interaction with Active OAM
   4.  OAM Interworking Models
     4.1.  OAM of DetNet MPLS Interworking with OAM of TSN
     4.2.  OAM of DetNet MPLS Interworking with OAM of DetNet IP
   5.  IANA Considerations
     5.1.  DetNet Associated Channel Header (d-ACH) Flags Registry
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   [RFC8655] introduces and explains Deterministic Networking (DetNet)
   architecture and how the Packet Replication, Elimination, and
   Ordering Functions (PREOF) can be used to ensure a low packet drop
   ratio in a DetNet domain.

   Operations, Administration, and Maintenance (OAM) protocols are used
   to detect and localize network defects and to monitor network
   performance.  Some OAM functions (e.g., failure detection) are
   usually performed proactively in the network, while others (e.g.,
   defect localization) are typically performed on demand.  These tasks
   can be achieved through a combination of active and hybrid OAM
   methods, as classified in [RFC7799].  This document presents a format
   for active OAM in DetNet networks with the MPLS data plane.

   Also, this document defines format and usage principles of the DetNet
   service Associated Channel over a DetNet network with the MPLS data
   plane [RFC8964].

2.  Conventions Used in This Document

2.1.  Terminology and Acronyms

   The term "DetNet OAM" in this document is used interchangeably with a
   "set of OAM protocols, methods, and tools for Deterministic
   Networking".

   BFD:  Bidirectional Forwarding Detection

   CFM:  Connectivity Fault Management

   d-ACH:  DetNet Associated Channel Header

   DetNet:  Deterministic Networking

   DetNet Node:  A node that is an actor in the DetNet domain.  Examples
      of DetNet nodes include DetNet domain edge nodes and DetNet nodes
      that perform PREOF within the DetNet domain.

   E2E:  End to end

   F-Label:  A DetNet "forwarding" label.  The F-Label identifies the
      Label Switched Path (LSP) used to forward a DetNet flow across an
      MPLS Packet Switched Network (PSN), e.g., a hop-by-hop label used
      between label switching routers.

   OAM:  Operations, Administration, and Maintenance

   PREOF:  Packet Replication, Elimination, and Ordering Functions

   PW:  Pseudowire

   S-Label:  A DetNet "service" label.  An S-Label is used between
      DetNet nodes that implement the DetNet service sub-layer
      functions.  An S-Label is also used to identify a DetNet flow at
      the DetNet service sub-layer.

   TSN:  Time-Sensitive Networking

   Underlay Network or Underlay Layer:  The network that provides
      connectivity between the DetNet nodes.  One example of an underlay
      layer is an MPLS network that provides LSP connectivity between
      DetNet nodes.

2.2.  Key Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Active OAM for DetNet Networks with the MPLS Data Plane

   OAM protocols and mechanisms act within the data plane of the
   particular networking layer; thus, it is critical that the data plane
   encapsulation supports OAM mechanisms that comply with the OAM
   requirements listed in [OAM-FRAMEWORK].

   Operation of a DetNet data plane with an MPLS underlay network is
   specified in [RFC8964].  Within the MPLS underlay network, DetNet
   flows are to be encapsulated analogous to pseudowires (PWs) as
   specified in [RFC3985] and [RFC4385].  For reference, the Generic PW
   MPLS Control Word (as defined in [RFC4385] and used with DetNet) is
   reproduced in Figure 1.


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |0 0 0 0|                Sequence Number                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: Generic PW MPLS Control Word Format

   PREOF in the DetNet domain is composed of a combination of nodes that
   perform replication and elimination functions.  The Elimination sub-
   function always uses the S-Label in conjunction with the packet
   sequencing information (i.e., the Sequence Number encoded in the
   DetNet Control Word).  The Replication sub-function uses the S-Label
   information only.

3.1.  DetNet Active OAM Encapsulation

   DetNet OAM, like PW OAM, uses the PW Associated Channel Header
   defined in [RFC4385].  At the same time, a DetNet PW can be viewed as
   a Multi-Segment PW, where DetNet service sub-layer functions are at
   the segment endpoints.  However, DetNet service sub-layer functions
   operate per packet level (not per segment).  These per-packet level
   characteristics of PREOF require additional fields for proper OAM
   packet processing.  MPLS encapsulation [RFC8964] of a DetNet active
   OAM packet is shown in Figure 2.


         +---------------------------------+
         |                                 |
         |        DetNet OAM Packet        |
         |                                 |
         +---------------------------------+ <--\
         | DetNet Associated Channel Header|    |
         +---------------------------------+    +--> DetNet active OAM
         |           S-Label               |    |    MPLS encapsulation
         +---------------------------------+    |
         |         [ F-Label(s) ]          |    |
         +---------------------------------+ <--/
         |           Data-Link             |
         +---------------------------------+
         |           Physical              |
         +---------------------------------+

     Figure 2: DetNet Active OAM Packet Encapsulation in the MPLS Data
                                   Plane

   Figure 3 displays encapsulation of a test packet for a DetNet active
   OAM protocol in case of MPLS over UDP/IP [RFC9025].


         +---------------------------------+
         |                                 |
         |        DetNet OAM Packet        |
         |                                 |
         +---------------------------------+ <--\
         | DetNet Associated Channel Header|    |
         +---------------------------------+    +--> DetNet active OAM
         |             S-Label             |    |    MPLS encapsulation
         +---------------------------------+    |
         |          [ F-label(s) ]         |    |
         +---------------------------------+ <--+
         |           UDP Header            |    |
         +---------------------------------+    +--> DetNet data plane
         |           IP Header             |    |    IP encapsulation
         +---------------------------------+ <--/
         |           Data-Link             |
         +---------------------------------+
         |           Physical              |
         +---------------------------------+

    Figure 3: DetNet Active OAM Packet Encapsulation in MPLS over UDP/IP

   Figure 4 displays the format of the DetNet Associated Channel Header
   (d-ACH).


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0 0 0 1|Version|Sequence Number|         Channel Type          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Node ID               |Level|  Flags  |Session|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Figure 4: d-ACH Format

   The d-ACH encodes the following fields:
      Bits 0..3:  These MUST be 0b0001.  This allows the packet to be
         distinguished from an IP packet [RFC4928] and from a DetNet
         data packet [RFC8964].

      Version:  A 4-bit field.  This document specifies version 0.

      Sequence Number:  An unsigned circular 8-bit field.  Because a
         DetNet active OAM test packet includes d-ACH, Section 4.2.1 of
         [RFC8964] does not apply to handling the Sequence Number field
         in DetNet OAM over the MPLS data plane.  The sequence number
         space is circular with no restriction on the initial value.
         The originator DetNet node MUST set the value of the Sequence
         Number field before the transmission of a packet.  The initial
         value SHOULD be random (unpredictable).  The originator node
         SHOULD increase the value of the Sequence Number field by 1 for
         each active OAM packet.  The originator MAY use other
         strategies, e.g., for negative testing of Packet Ordering
         Functions.

      Channel Type:  A 16-bit field and the value of the DetNet
         Associated Channel Type.  It MUST be one of the values listed
         in the IANA "MPLS Generalized Associated Channel (G-ACh) Types
         (including Pseudowire Associated Channel Types)" registry
         [IANA-G-ACh-Types].

      Node ID:  An unsigned 20-bit field.  The value of the Node ID
         field identifies the DetNet node that originated the packet.  A
         DetNet node MUST be provisioned with a Node ID that is unique
         in the DetNet domain.  Methods for distributing Node ID are
         outside the scope of this specification.

      Level:  A 3-bit field.  Semantically, the Level field is analogous
         to the Maintenance Domain Level in [IEEE.802.1Q].  The Level
         field is used to cope with the "all active path forwarding"
         (defined by the TSN Task Group of the IEEE 802.1 WG
         [IEEE802.1TSNTG]) characteristics of the PREOF concept.  A
         hierarchical relationship between OAM domains can be created
         using the Level field value, as illustrated by Figure 18.7 in
         [IEEE.802.1Q].

      Flags:  A 5-bit field.  The Flags field contains five 1-bit flags.
         Section 5.1 creates the IANA "DetNet Associated Channel Header
         (d-ACH) Flags" registry for new flags to be defined.  The flags
         defined in this specification are presented in Figure 5.

      Session ID:  A 4-bit field.  The Session field distinguishes OAM
         sessions originating from the same node (a given Maintenance
         End Point may have multiple simultaneously active OAM sessions)
         at the given Level.


          0 1 2 3 4
         +-+-+-+-+-+
         |U|U|U|U|U|
         +-+-+-+-+-+

          Figure 5: DetNet Associated Channel Header Flags Field Format

   U:  Unused and for future use.  MUST be 0 on transmission and ignored
      on receipt.

   According to [RFC8964], a DetNet flow is identified by the S-Label
   that MUST be at the bottom of the stack.  An active OAM packet MUST
   include d-ACH immediately following the S-Label.

3.2.  DetNet PREOF Interaction with Active OAM

   At the DetNet service sub-layer, special functions (notably PREOF)
   MAY be applied to the particular DetNet flow to potentially reduce
   packet loss, improve the probability of on-time packet delivery, and
   ensure in-order packet delivery.  PREOF relies on sequencing
   information in the DetNet service sub-layer.  For a DetNet active OAM
   packet, PREOF MUST use the Sequence Number field value as the source
   of this sequencing information.  App-flow and OAM use different
   sequence number spaces.  PREOF algorithms are executed with respect
   to the sequence number space identified by the flow's characteristic
   information.  Although the Sequence Number field in d-ACH has a range
   from 0 through 255, it provides sufficient space because the rate of
   DetNet active OAM packets is significantly lower compared to the rate
   of DetNet packets in an App-flow; therefore, wrapping around is not
   an issue.

4.  OAM Interworking Models

   Interworking of two OAM domains that utilize different networking
   technology can be realized by either a peering model or a tunneling
   model.  In a peering model, OAM domains are within the corresponding
   network domain.  When using the peering model, state changes that are
   detected by a Fault Management OAM protocol can be mapped from one
   OAM domain into another or a notification, e.g., an alarm can be sent
   to a central controller.  In the tunneling model of OAM interworking,
   usually only one active OAM protocol is used.  Its test packets are
   tunneled through another domain along with the data flow, thus
   ensuring fate sharing among test and data packets.

4.1.  OAM of DetNet MPLS Interworking with OAM of TSN

   DetNet active OAM can provide end-to-end (E2E) fault management and
   performance monitoring for a DetNet flow.  In the case of DetNet with
   an MPLS data plane and an IEEE 802.1 Time-Sensitive Networking (TSN)
   sub-network, it implies the interworking of DetNet active OAM with
   TSN OAM, of which the data plane aspects are specified in [RFC9037].

   When the peering model (Section 4) is used in the Connectivity Fault
   Management (CFM) OAM protocol [IEEE.802.1Q], the node that borders
   both TSN and DetNet MPLS domains MUST support [RFC7023].  [RFC7023]
   specifies the mapping of defect states between Ethernet Attachment
   Circuits and associated Ethernet PWs that are part of an E2E emulated
   Ethernet service and are also applicable to E2E OAM across DetNet
   MPLS and TSN domains.  The CFM [IEEE.802.1Q] [ITU.Y1731] can provide
   fast detection of a failure in the TSN segment of the DetNet service.
   In the DetNet MPLS domain, Bidirectional Forwarding Detection (BFD),
   as specified in [RFC5880] and [RFC5885], can be used.  To provide E2E
   failure detection, the TSN and DetNet MPLS segments could be treated
   as concatenated such that the diagnostic codes (see Section 6.8.17 of
   [RFC5880]) MAY be used to inform the upstream DetNet MPLS node of a
   TSN segment failure.  Performance monitoring can be supported by
   [RFC6374] in the DetNet MPLS and by [ITU.Y1731] in TSN domains,
   respectively.  Performance objectives for each domain should refer to
   metrics that are composable [RFC6049] or are defined for each domain
   separately.

   The following considerations apply when using the tunneling model of
   OAM interworking between DetNet MPLS and TSN domains based on general
   principles described in Section 4 of [RFC9037]:

   *  Active OAM test packets MUST be mapped to the same TSN Stream ID
      as the monitored DetNet flow.

   *  Active OAM test packets MUST be processed in the TSN domain based
      on their S-Label and Class of Service marking (the Traffic Class
      field value).

   Mapping between a DetNet flow and TSN Stream in the TSN sub-network
   is described in Section 4.1 of [RFC9037].  The mapping has to be done
   only on the edge node of the TSN sub-network, and intermediate TSN
   nodes do not need to recognize the S-Label.  An edge node has two
   components:

   1.  A passive Stream identification function.

   2.  An active Stream identification function.

   The first component identifies the DetNet flow (using Clause 6.8 of
   [IEEE.802.1CBdb]), and the second component creates the TSN Stream by
   manipulating the Ethernet header.  That manipulation simplifies the
   identification of the TSN Stream in the intermediate TSN nodes by
   avoiding the need for them to look outside of the Ethernet header.
   DetNet MPLS OAM packets use the same S-Label as the DetNet flow data
   packets.  The above-described mapping function treats these OAM
   packets as data packets of the DetNet flow.  As a result, DetNet MPLS
   OAM packets are fate sharing within the TSN sub-network.  As an
   example of the mapping between DetNet MPLS and TSN, see Annex C.1 of
   [IEEE.802.1CBdb] that, in support of [RFC9037], describes how to
   match MPLS DetNet flows and achieve TSN Streams.

   Note that the tunneling model of the OAM interworking requires that
   the remote peer of the E2E OAM domain supports the active OAM
   protocol selected on the ingress endpoint.  For example, if BFD is
   used for proactive path continuity monitoring in the DetNet MPLS
   domain, BFD support (as defined in [RFC5885]) is necessary at any TSN
   endpoint of the DetNet service.

4.2.  OAM of DetNet MPLS Interworking with OAM of DetNet IP

   Interworking between active OAM segments in DetNet MPLS and DetNet IP
   domains can also be realized using either the peering model or the
   tunneling model, as discussed in Section 4.1.  Using the same
   protocol, e.g., BFD over both segments, simplifies the mapping of
   errors in the peering model.  For example, respective BFD sessions in
   DetNet MPLS and DetNet IP domains can be in a concatenated
   relationship as described in Section 6.8.17 of [RFC5880].  To provide
   performance monitoring over a DetNet IP domain, the Simple Two-way
   Active Measurement Protocol (STAMP) [RFC8762] and its extensions
   [RFC8972] can be used to measure packet loss and packet delay
   metrics.  Such performance metrics can be used to calculate
   composable metrics [RFC6049] within DetNet MPLS and DetNet IP domains
   to reflect the end-to-end DetNet service performance.

5.  IANA Considerations

5.1.  DetNet Associated Channel Header (d-ACH) Flags Registry

   IANA has created the "DetNet Associated Channel Header (d-ACH) Flags"
   registry within the "DetNet Associated Channel Header (d-ACH) Flags"
   registry group.  The registration procedure is "IETF Review"
   [RFC8126].  There are five flags in the 5-bit Flags field, as defined
   in Table 1.

                            +=====+=============+
                            | Bit | Description |
                            +=====+=============+
                            | 0-4 | Unassigned  |
                            +-----+-------------+

                               Table 1: DetNet
                              Associated Channel
                             Header (d-ACH) Flags
                                   Registry

6.  Security Considerations

   Security considerations discussed in DetNet specifications [RFC8655],
   [RFC8964], [RFC9055], and [OAM-FRAMEWORK] are applicable to this
   document.  Security concerns and issues related to MPLS OAM tools
   like LSP Ping [RFC8029] and BFD over PW [RFC5885] also apply to this
   specification.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC7023]  Mohan, D., Ed., Bitar, N., Ed., Sajassi, A., Ed., DeLord,
              S., Niger, P., and R. Qiu, "MPLS and Ethernet Operations,
              Administration, and Maintenance (OAM) Interworking",
              RFC 7023, DOI 10.17487/RFC7023, October 2013,
              <https://www.rfc-editor.org/info/rfc7023>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,
              <https://www.rfc-editor.org/info/rfc8655>.

   [RFC8964]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
              S., and J. Korhonen, "Deterministic Networking (DetNet)
              Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
              2021, <https://www.rfc-editor.org/info/rfc8964>.

   [RFC9025]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
              Bryant, "Deterministic Networking (DetNet) Data Plane:
              MPLS over UDP/IP", RFC 9025, DOI 10.17487/RFC9025, April
              2021, <https://www.rfc-editor.org/info/rfc9025>.

7.2.  Informative References

   [IANA-G-ACh-Types]
              IANA, "MPLS Generalized Associated Channel (G-ACh) Types
              (including Pseudowire Associated Channel Types)",
              <https://www.iana.org/assignments/g-ach-parameters/>.

   [IEEE.802.1CBdb]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks--Frame Replication and Elimination for
              Reliability--Amendment 2: Extended Stream Identification
              Functions", IEEE Std 802.1CBdb-2021, December 2021.

   [IEEE.802.1Q]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Network--Bridges and Bridged Networks", IEEE Std 802.1Q-
              2018, DOI 10.1109/IEEESTD.2018.8403927, July 2018,
              <https://doi.org/10.1109/IEEESTD.2018.8403927>.

   [IEEE802.1TSNTG]
              IEEE 802.1, "Time-Sensitive Networking (TSN) Task Group",
              TSN Standards, <https://1.ieee802.org/tsn/>.

   [ITU.Y1731]
              ITU-T, "Operation, administration and maintenance (OAM)
              functions and mechanisms for Ethernet-based networks",
              ITU-T Recommendation G.8013/Y.1731, June 2023.

   [OAM-FRAMEWORK]
              Mirsky, G., Theoleyre, F., Papadopoulos, G. Z., Bernardos,
              CJ., Varga, B., and J. Farkas, "Framework of Operations,
              Administration and Maintenance (OAM) for Deterministic
              Networking (DetNet)", Work in Progress, Internet-Draft,
              draft-ietf-detnet-oam-framework-11, 8 January 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
              oam-framework-11>.

   [RFC3985]  Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
              Edge-to-Edge (PWE3) Architecture", RFC 3985,
              DOI 10.17487/RFC3985, March 2005,
              <https://www.rfc-editor.org/info/rfc3985>.

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
              February 2006, <https://www.rfc-editor.org/info/rfc4385>.

   [RFC4928]  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
              Cost Multipath Treatment in MPLS Networks", BCP 128,
              RFC 4928, DOI 10.17487/RFC4928, June 2007,
              <https://www.rfc-editor.org/info/rfc4928>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

   [RFC5885]  Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
              Forwarding Detection (BFD) for the Pseudowire Virtual
              Circuit Connectivity Verification (VCCV)", RFC 5885,
              DOI 10.17487/RFC5885, June 2010,
              <https://www.rfc-editor.org/info/rfc5885>.

   [RFC6049]  Morton, A. and E. Stephan, "Spatial Composition of
              Metrics", RFC 6049, DOI 10.17487/RFC6049, January 2011,
              <https://www.rfc-editor.org/info/rfc6049>.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <https://www.rfc-editor.org/info/rfc6374>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

   [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
              Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
              Switched (MPLS) Data-Plane Failures", RFC 8029,
              DOI 10.17487/RFC8029, March 2017,
              <https://www.rfc-editor.org/info/rfc8029>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
              Two-Way Active Measurement Protocol", RFC 8762,
              DOI 10.17487/RFC8762, March 2020,
              <https://www.rfc-editor.org/info/rfc8762>.

   [RFC8972]  Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A.,
              and E. Ruffini, "Simple Two-Way Active Measurement
              Protocol Optional Extensions", RFC 8972,
              DOI 10.17487/RFC8972, January 2021,
              <https://www.rfc-editor.org/info/rfc8972>.

   [RFC9037]  Varga, B., Ed., Farkas, J., Malis, A., and S. Bryant,
              "Deterministic Networking (DetNet) Data Plane: MPLS over
              IEEE 802.1 Time-Sensitive Networking (TSN)", RFC 9037,
              DOI 10.17487/RFC9037, June 2021,
              <https://www.rfc-editor.org/info/rfc9037>.

   [RFC9055]  Grossman, E., Ed., Mizrahi, T., and A. Hacker,
              "Deterministic Networking (DetNet) Security
              Considerations", RFC 9055, DOI 10.17487/RFC9055, June
              2021, <https://www.rfc-editor.org/info/rfc9055>.

Acknowledgments

   The authors extend their appreciation to Pascal Thubert for his
   insightful comments and productive discussion that helped to improve
   the document.  The authors are enormously grateful to János Farkas
   for his detailed comments and the inspiring discussion that made this
   document clearer and stronger.  The authors recognize helpful reviews
   and suggestions from Andrew Malis, David Black, Tianran Zhou, and
   Kiran Makhijani.  And special thanks to Ethan Grossman for his
   fantastic help in improving the document.

Authors' Addresses

   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com


   Mach(Guoyi) Chen
   Huawei
   Email: mach.chen@huawei.com


   Balazs Varga
   Ericsson
   Budapest
   Magyar Tudosok krt. 11.
   1117
   Hungary
   Email: balazs.a.varga@ericsson.com